The present invention relates to a radial shaft seal which includes a supporting ring which is attached to at least one sealing ring made of a polymer material, where the sealing ring has at least one sealing lip and an additional gasket is arranged on the side of the sealing lip facing away from the space to be sealed.
Such a radial shaft seal is known from German Patent 867189. The additional gasket described therein is designed as a dust seal and is held in a rotationally fixed manner in a multipart gasket housing. The multipart gasket housing has a pressure ring and a spacer ring which applies tension to the supporting ring with the metallic housing jacket. A felt washer designed as a dust seal is arranged between a radial wall of the housing jacket and the supporting ring or an elastomer coating of the supporting ring, where the supporting ring or the coating is designed with a nubby grip element for the felt washer. However, it should be pointed out that the previously known radial shaft seal is composed of a number of individual parts that must be assembled, which is not very satisfactory from the standpoint of both economy and manufacturing technology.
The object of the present invention is to further develop a radial shaft seal of the type noted above such that it is made of fewer individual parts and can be manufactured less expensively and more easily from the standpoint of economy and manufacturing technology.
To achieve this object, the supporting ring is designed in one piece and has two radial projections arranged next to one another with an axial distance between them, and a circular additional gasket produced separately is arranged without adhesion in the gap formed by this distance and is under axial tension. Such a radial shaft seal has a simple design and can be produced inexpensively and without problem. The radial projections form a one-piece component of the supporting ring on which the sealing ring is integrally molded. The supporting ring is preferably made of a metal material.
The first radial projection facing the space to be sealed is preferably covered at least partially by a coating of polymer material on the side facing the second radial projection, where the additional gasket is under axial tension with the coating. Such a radial shaft seal is produced by the fact that after vulcanization of the polymer material on the supporting ring, the second radial projection is flanged toward the inside with the insertion of the additional gasket from the axial direction first to the radial direction such that the additional gasket is arranged under an axial tension between the second radial projection and the coating. In combination with the axial tension with which the additional gasket is arranged between the two radial projections, the coefficient of friction of the polymer, preferably elastomer, material of the coating causes a rotationally fixed arrangement of the additional gasket relative to the supporting ring. There is a relative movement of the additional gasket which is subject to friction only on the surface to be sealed.
The additional gasket is preferably made of an open-pore filter material, such as a nonwoven. It is advantageous here for the additional gasket to be permeable to air, so there is no possibility of a vacuum developing between the additional gasket and the sealing lip. The air permeability of the additional gasket has proven especially advantageous if the sealing lip of the sealing ring is provided with a reverse twist to return the medium to be sealed, which is used for cooling and lubrication of the sealing lip, back in the direction of the space to be sealed. Even with a reverse conveyance of the medium to be sealed in the direction of the space to be sealed, no vacuum develops between the additional gasket and the sealing lip relative to the environment. Therefore, the seal remains good during a long service life of the radial shaft seal.
The sealing ring and the coating are preferably each made of an elastomer material. Suitable materials include preferably acrylate rubber (ACM) or fluoropolymers (FPM). The advantage of a sealing ring and a coating of ACM is that the costs are lower than when using FPM and efficiency is good.
However, it is advantageous that when using FPM, the service life is increased with a very good efficiency.
Depending on the use conditions, it is also possible to use the materials acrylonitrile butadiene rubber (NBR), silicone rubber (MVQ), polytetrafluoroethylene (PTFE) or combinations thereof.
Production of the radial shaft seal according to the present invention is simplified if the sealing ring and the coating are each made of the same material and are designed in one piece, with one developing into the other. Both the sealing ring and the coating can then be molded at the same time onto the supporting ring especially easily in one operation and then vulcanized.
Depending on the respective application, however, there is also the possibility that the sealing ring and the coating are made of different elastomer materials. Despite the different materials in such a case it is also possible to mold the different materials onto the supporting ring at the same time and to vulcanize them.
The supporting ring is preferably made of a deep-drawable metal material. The supporting ring can then be manufactured easily and inexpensively. A very stable bond is obtained after vulcanization of an elastomer material for the sealing ring and the coating. Alternatively, other tough materials such as polymer materials may also be used to manufacture the supporting ring.
The first radial projection may be attached to a first axial projection on the inside radially and the second radial projection may be attached to a second axial projection on the outside radially, with the axial projections being designed so that they develop into one another through a 180xc2x0 arc on the side facing away from the radial projections.
The inner circumference of the second axial projection is preferably in contact with the outer circumference of the first axial projection. The supporting ring thus has extremely good dimensional stability, which is especially advantageous with regard to providing an accurate allocation of the two radial projections and the additional gasket arranged between them under axial tension.
The outer circumference of the additional gasket is in contact with the inner circumference of the second axial projection. This ensures good centering of the additional gasket.
Due to the arrangement of the additional gasket between the two radial projections without adhesion, where the additional gasket is held exclusively by axial tension, it is generally advantageous that no problems occur due to bonding of the additional gasket in manufacturing the radial shaft seal. Since the additional gasket is not glued, the bonding cannot be loosened when the radial shaft seal is exposed to high temperatures and aggressive media.